The present invention relates to an excavator for excavating ground and constructing underground continuous, draining and retaining vertical wall-shaped structures of a hardening liquid-excavated ground earth mixture or ready-mixed concrete or sand, especially to control a ground gas and water flow and to provide a drainage, isolation, containment and separation of subsurface environments, prevention of a leakage through such walls and isolation of contaminated and sensitive areas, as anchors and foundations, and to underground continuous wall-shaped structure construction methods utilizing the excavators in civil engineering and construction works.
In constructing an underground wall according to a prior art technique, first a hole of an elliptical cross-section having a 2 to 3 m major axis is dug in the ground to a predetermined depth by a powerful bucket or by two or three series of auger drills.
In constructing an underground wall according to a prior art technique, first a hole of an elliptical cross-section having a 2 to 3 m major axis is dug in the ground to a predetermined depth by a powerful bucket or by two or three series of auger drills. After the hole formed in slurry is sealed with a bentonite solution to prevent further penetration of slurry, a reinforcing bar cage is placed in the groove and a ready mixed concrete is then poured into the groove to form a foundation column. Such method is repeated to form an underground continuous wall. Slurry or bentonite solution layers interrupt the formation of the continuous wall so that after completion of the wall, ground water tends to leak into the inside of the continuous walls through the joints. It is therefore very difficult to provide the underground continuous wall simultaneously having two functions as foundation wall and a diaphragm wall.
U.S. Pat. No. 5,244,315 discloses an excavator for constructing an underground continuous wall that includes a travelling trolley, supporting frames, an endless chain cutter and agitator. The cutter excavates a trench, jets a hardening liquid in an excavated groove and mixes the liquid with the earth and sand in the groove to form a soil cement wall. Significant defects of the excavator and method of its advancement are: it is very difficult to form a deep wall in the stony ground and a horizontal stratum; the cantilever endless chain cutter being advanced that requires a huge traction force and stabilizing moment applied to the trolley; the cutter is not capable to compact the filling wall being formed and for forming a compacted running filling there is needed much more hardening liquid.
U.S. Pat. No. 5,685,668 for Barrier Wall Installation System discloses an excavator for delivering an unrolling liner material into and along a trench being formed of a depth up to sixty feet that prevents side wall collapse in a surface water saturated zone and forms a barrier wall. Significant defects of that barrier wall installation system are the similar as shown above and following: the wall may be shaped into system are the similar as shown above and following: the wall may be shaped into plane and vertical cylindrical surfaces only because of the cylindrical shape of a roll of the liner material; it is difficult to use a wide liner material of a width that is sufficient to reach a first confining bed.